The present invention relates to a technique for producing an absorbent article. More particularly, the invention relates to a method and apparatus for forming a stabilized absorbent web.
Absorbent articles and structures, such as absorbent pads and absorbent cores, have been formed by employing various techniques, such as wet forming techniques, and air laying techniques. Conventional air laying techniques have transported a foraminous forming surface, such as a forming screen, through a forming chamber. Fibrous materials and particulate materials have been introduced into the forming chamber, and a vacuum source has been employed to draw an air stream through the forming surface. The air stream entrains the fibers and particulate material for deposition onto the moving forming surface.
Conventional distribution devices, such as nozzles, have been employed to deliver particulate material in desired regions along the thickness dimension of an airlaid fibrous web. Conventional devices have also been employed to distribute binder materials into an airlaid fibrous web. Such conventional processes and apparatus have been employed to combine binder fibers into an airlaid fibrous web, and in particular arrangements, the binder fibers have been composed of synthetic polymers.
In other conventional systems, multiple forming chambers have been employed to form different layers of material in a composite absorbent article. The different layers may be composed of different types of fibrous material, and different types of particulate material.
Conventional techniques, such as those described above, have been excessively complex and costly. When such conventional techniques have been employed to construct absorbent structures with high wet-strength, the structures have been excessively stiff, and have required the incorporation of excessive amounts of expensive materials. In addition, the resulting structures have suffered an excessive degradation in absorption properties, particularly excessive reductions in the rate of absorption. As a result, there has been a continued need for improved techniques for generating an absorbent structure having desired combinations of softness, strength and absorbency.
The present invention provides a distinctive method and apparatus for forming a stabilized absorbent article. In the method aspect of the invention, a process for forming an absorbent web can include an airlaying of a first fibrous stratum, and an airlaying of an intermediate fibrous stratum onto the first fibrous stratum. A liquid, wet-strength agent is distributed onto fibers of the intermediate fibrous stratum, and at least a second fibrous stratum is airlaid onto the intermediate fibrous stratum. The method is configured to operatively form or join the intermediate fibrous stratum with at least the first fibrous stratum, and render the intermediate fibrous stratum substantially non-dispersible. Desirably, the method operatively joins the first and second fibrous strata to the intermediate fibrous stratum. In a particular aspect, the strata of the web can be operatively compressed prior to curing the wet-strength agent. In another aspect, the liquid wet-strength agent can be distributed onto the fibers of the intermediate fibrous stratum during the airlaying of the intermediate fibrous stratum.
Generally stated, the apparatus for forming an absorbent web includes a fiber source which can supply fibers for airlaying onto a forming surface to provide a first fibrous stratum, a second fibrous stratum, and an intermediate fibrous stratum that is interposed between the first and second fibrous strata. The apparatus includes a mechanism, such as a nozzle, which can distribute a liquid, wet-strength agent onto fibers of the intermediate fibrous stratum. The apparatus is operatively configured to operatively form or join the intermediate fibrous stratum with at least the first fibrous stratum, and render the intermediate fibrous stratum substantially non-dispersible in liquid. In a particular aspect, a web compactor can operatively compress the strata of the web prior to curing the wet-strength agent. In another aspect, the nozzle can distribute the liquid wet-strength agent onto the fibers of the intermediate fibrous stratum during the airlaying of the intermediate fibrous stratum.
In its various aspects and configurations, the method and apparatus of the present invention can advantageously provide an efficient and low cost technique which forms a distinctively stratified absorbent web by employing an airlaying operation. The technique can more efficiently utilize a wet-strength agent to provide a sufficiently high strength while incorporating a relatively small quantity of the wet-strength agent. Additionally, the technique can reliably and efficiently locate the wet-strength agent in an intermediate stratum to help maintain desired levels of softness in other strata of the absorbent structure. The process and apparatus of the invention can also distribute the wet-strength agent with an system that is less susceptible to clogging. As a result, the technique of the invention can more efficiently produce an absorbent structure having desired combinations of dry strength, wet strength, softness, flexibility and liquid distribution.